[libc++] Simplify the implementation of std::get for pairs (#114984)
This makes it clearer what the functions actually do. As a nice
side-effect it also avoids a function call. If the C++03 header split is
successful we could drop `__get_pair` entirely.
diff --git a/libcxx/include/__utility/pair.h b/libcxx/include/__utility/pair.h
index 99b0eb9..ab390aa 100644
--- a/libcxx/include/__utility/pair.h
+++ b/libcxx/include/__utility/pair.h
@@ -654,42 +654,42 @@
#if _LIBCPP_STD_VER >= 14
template <class _T1, class _T2>
inline _LIBCPP_HIDE_FROM_ABI constexpr _T1& get(pair<_T1, _T2>& __p) _NOEXCEPT {
- return __get_pair<0>::get(__p);
+ return __p.first;
}
template <class _T1, class _T2>
inline _LIBCPP_HIDE_FROM_ABI constexpr _T1 const& get(pair<_T1, _T2> const& __p) _NOEXCEPT {
- return __get_pair<0>::get(__p);
+ return __p.first;
}
template <class _T1, class _T2>
inline _LIBCPP_HIDE_FROM_ABI constexpr _T1&& get(pair<_T1, _T2>&& __p) _NOEXCEPT {
- return __get_pair<0>::get(std::move(__p));
+ return std::forward<_T1&&>(__p.first);
}
template <class _T1, class _T2>
inline _LIBCPP_HIDE_FROM_ABI constexpr _T1 const&& get(pair<_T1, _T2> const&& __p) _NOEXCEPT {
- return __get_pair<0>::get(std::move(__p));
+ return std::forward<_T1 const&&>(__p.first);
}
-template <class _T1, class _T2>
-inline _LIBCPP_HIDE_FROM_ABI constexpr _T1& get(pair<_T2, _T1>& __p) _NOEXCEPT {
- return __get_pair<1>::get(__p);
+template <class _T2, class _T1>
+inline _LIBCPP_HIDE_FROM_ABI constexpr _T2& get(pair<_T1, _T2>& __p) _NOEXCEPT {
+ return __p.second;
}
-template <class _T1, class _T2>
-inline _LIBCPP_HIDE_FROM_ABI constexpr _T1 const& get(pair<_T2, _T1> const& __p) _NOEXCEPT {
- return __get_pair<1>::get(__p);
+template <class _T2, class _T1>
+inline _LIBCPP_HIDE_FROM_ABI constexpr _T2 const& get(pair<_T1, _T2> const& __p) _NOEXCEPT {
+ return __p.second;
}
-template <class _T1, class _T2>
-inline _LIBCPP_HIDE_FROM_ABI constexpr _T1&& get(pair<_T2, _T1>&& __p) _NOEXCEPT {
- return __get_pair<1>::get(std::move(__p));
+template <class _T2, class _T1>
+inline _LIBCPP_HIDE_FROM_ABI constexpr _T2&& get(pair<_T1, _T2>&& __p) _NOEXCEPT {
+ return std::forward<_T2&&>(__p.second);
}
-template <class _T1, class _T2>
-inline _LIBCPP_HIDE_FROM_ABI constexpr _T1 const&& get(pair<_T2, _T1> const&& __p) _NOEXCEPT {
- return __get_pair<1>::get(std::move(__p));
+template <class _T2, class _T1>
+inline _LIBCPP_HIDE_FROM_ABI constexpr _T2 const&& get(pair<_T1, _T2> const&& __p) _NOEXCEPT {
+ return std::forward<_T2 const&&>(__p.second);
}
#endif // _LIBCPP_STD_VER >= 14
diff --git a/libcxx/test/std/utilities/utility/pairs/pair.astuple/pairs.by.type.pass.cpp b/libcxx/test/std/utilities/utility/pairs/pair.astuple/pairs.by.type.pass.cpp
index f6940c4..6d1dc9f 100644
--- a/libcxx/test/std/utilities/utility/pairs/pair.astuple/pairs.by.type.pass.cpp
+++ b/libcxx/test/std/utilities/utility/pairs/pair.astuple/pairs.by.type.pass.cpp
@@ -8,43 +8,114 @@
// UNSUPPORTED: c++03, c++11
-#include <utility>
-#include <string>
-#include <type_traits>
+#include <cassert>
#include <complex>
#include <memory>
-
-#include <cassert>
+#include <type_traits>
+#include <utility>
#include "test_macros.h"
-int main(int, char**)
-{
+TEST_CONSTEXPR_CXX14 bool test() {
+ { // Make sure that references work as expected
+ int i = 1;
+ int j = 2;
+
+ {
+ std::pair<int&, int&&> p(i, std::move(j));
+ assert(&std::get<int&>(p) == &i);
+ assert(&std::get<int&&>(p) == &j);
+
+ assert(&std::get<int&>(std::move(p)) == &i);
+ assert(std::get<int&&>(std::move(p)) == 2);
+
+ const std::pair<int&, int&&> cp(i, std::move(j));
+ assert(&std::get<int&>(cp) == &i);
+ assert(&std::get<int&&>(cp) == &j);
+
+ assert(&std::get<int&>(std::move(cp)) == &i);
+ assert(std::get<int&&>(std::move(cp)) == 2);
+ }
+
+ {
+ std::pair<int&&, int&> p(std::move(i), j);
+ assert(&std::get<int&>(p) == &j);
+ assert(&std::get<int&&>(p) == &i);
+
+ assert(&std::get<int&>(std::move(p)) == &j);
+ assert(std::get<int&&>(std::move(p)) == 1);
+
+ const std::pair<int&&, int&> cp(std::move(i), j);
+ assert(&std::get<int&>(cp) == &j);
+ assert(&std::get<int&&>(cp) == &i);
+
+ assert(&std::get<int&>(std::move(cp)) == &j);
+ assert(std::get<int&&>(std::move(cp)) == 1);
+ }
+ }
+
+ {
typedef std::complex<float> cf;
- {
- auto t1 = std::make_pair<int, cf> ( 42, { 1,2 } );
- assert ( std::get<int>(t1) == 42 );
- assert ( std::get<cf>(t1).real() == 1 );
- assert ( std::get<cf>(t1).imag() == 2 );
- }
+ auto t1 = std::make_pair<int, cf>(42, {1, 2});
+ assert(std::get<int>(t1) == 42);
+ assert(std::get<cf>(t1).real() == 1);
+ assert(std::get<cf>(t1).imag() == 2);
+ }
- {
- const std::pair<int, const int> p1 { 1, 2 };
- const int &i1 = std::get<int>(p1);
- const int &i2 = std::get<const int>(p1);
- assert ( i1 == 1 );
- assert ( i2 == 2 );
- }
+ {
+ const std::pair<int, const int> p1{1, 2};
+ const int& i1 = std::get<int>(p1);
+ const int& i2 = std::get<const int>(p1);
+ assert(i1 == 1);
+ assert(i2 == 2);
+ }
- {
+ {
+ int x = 42;
+ int const y = 43;
+ std::pair<int&, int const&> const p(x, y);
+ static_assert(std::is_same<int&, decltype(std::get<int&>(std::move(p)))>::value, "");
+ static_assert(noexcept(std::get<int&>(std::move(p))), "");
+ static_assert(std::is_same<int const&, decltype(std::get<int const&>(std::move(p)))>::value, "");
+ static_assert(noexcept(std::get<int const&>(std::move(p))), "");
+ }
+
+ {
+ int x = 42;
+ int const y = 43;
+ std::pair<int&&, int const&&> const p(std::move(x), std::move(y));
+ static_assert(std::is_same<int&&, decltype(std::get<int&&>(std::move(p)))>::value, "");
+ static_assert(noexcept(std::get<int&&>(std::move(p))), "");
+ static_assert(std::is_same<int const&&, decltype(std::get<int const&&>(std::move(p)))>::value, "");
+ static_assert(noexcept(std::get<int const&&>(std::move(p))), "");
+ }
+
+ {
+ constexpr const std::pair<int, const int> p{1, 2};
+ static_assert(std::get<int>(std::move(p)) == 1, "");
+ static_assert(std::get<const int>(std::move(p)) == 2, "");
+ }
+
+ return true;
+}
+
+int main(int, char**) {
+ test();
+#if TEST_STD_VER >= 14
+ static_assert(test(), "");
+#endif
+
+ // These tests use types which only work during constant evaluation in very recent standards
+
+ {
typedef std::unique_ptr<int> upint;
std::pair<upint, int> t(upint(new int(4)), 42);
upint p = std::get<upint>(std::move(t)); // get rvalue
assert(*p == 4);
assert(std::get<upint>(t) == nullptr); // has been moved from
- }
+ }
- {
+ {
typedef std::unique_ptr<int> upint;
const std::pair<upint, int> t(upint(new int(4)), 42);
static_assert(std::is_same<const upint&&, decltype(std::get<upint>(std::move(t)))>::value, "");
@@ -52,37 +123,11 @@
static_assert(std::is_same<const int&&, decltype(std::get<int>(std::move(t)))>::value, "");
static_assert(noexcept(std::get<int>(std::move(t))), "");
auto&& p = std::get<upint>(std::move(t)); // get const rvalue
- auto&& i = std::get<int>(std::move(t)); // get const rvalue
+ auto&& i = std::get<int>(std::move(t)); // get const rvalue
assert(*p == 4);
assert(i == 42);
assert(std::get<upint>(t) != nullptr);
- }
-
- {
- int x = 42;
- int const y = 43;
- std::pair<int&, int const&> const p(x, y);
- static_assert(std::is_same<int&, decltype(std::get<int&>(std::move(p)))>::value, "");
- static_assert(noexcept(std::get<int&>(std::move(p))), "");
- static_assert(std::is_same<int const&, decltype(std::get<int const&>(std::move(p)))>::value, "");
- static_assert(noexcept(std::get<int const&>(std::move(p))), "");
- }
-
- {
- int x = 42;
- int const y = 43;
- std::pair<int&&, int const&&> const p(std::move(x), std::move(y));
- static_assert(std::is_same<int&&, decltype(std::get<int&&>(std::move(p)))>::value, "");
- static_assert(noexcept(std::get<int&&>(std::move(p))), "");
- static_assert(std::is_same<int const&&, decltype(std::get<int const&&>(std::move(p)))>::value, "");
- static_assert(noexcept(std::get<int const&&>(std::move(p))), "");
- }
-
- {
- constexpr const std::pair<int, const int> p { 1, 2 };
- static_assert(std::get<int>(std::move(p)) == 1, "");
- static_assert(std::get<const int>(std::move(p)) == 2, "");
- }
+ }
return 0;
}
